Your baby's first poop will be meconium, a tar-like, blackish-green substance that you'll see for a couple of days. After the meconium runs its course, greenish-brown transitional stools follow; by the fourth or fifth day, breastfed babies pass yellowish, seedy poop, while formula-fed infants' stool is denser and ranges in color from yellow to brown-green.
Expect variation in how often your infant has bowel movements. A formula-fed infant may poop three or four times a day, while a breastfed infant may go after every feeding or as infrequently as once a week. --Sharon Anne Waldrop
Originally published in American Baby magazine, November 2007.